When a given geographic area is provided with radar coverage using a passive radar, the main problem that presents itself consists of the difficulty that is encountered in jointly using the information generated from the received signals, bearing in mind that these signals may originate from one or other of the utility transmitters, the transmissions of which partially or totally cover the area observed by the radar.
Generally, this information is embodied, as is known, in the form of tracks which show the progression in the space observed of the objects of interest detected by the radar.
Also generally, the tracks generated by the radar are maintained by the blips supplied periodically by the radar concerned. A blip represents the information extracted from the received signals. This information comprises in particular the speed and position information concerning, for a given measurement instant, the characteristics of an object detected by this radar. All the successive blips formed over time for one and the same detected object are thus used to form and maintain the track itself, a track being able to be analyzed manually via a display system, or automatically. In this way, at each measurement instant, the radar receives signals emanating from one or other of the utility transmitters, each transmitter transmitting on a frequency band that is generally distinct. This band is also likely to consist of a number of separate subbands, or channels, operated simultaneously by the transmitter. In such a case, the receiver of the radar forms a number of reception channels that is appropriate to the reception of all the channels covered by all the transmitters.
As is known, the radar then separately processes the signal received on each channel and generates, for each channel, and for each object detected, a blip which is associated, as appropriate, with the blips relating to the same object and generated at the preceding measurement instants. The succession of the blips forms the track relating to the object detected for the channel concerned.
Consequently, one and the same object located in a portion of the space covered by the transmissions of a number of utility transmitters may be detected by the radar on a number of reception channels. Thus, by combining the information generated from the various reception channels, it is possible to refine the determination of the parameters characterizing the object detected.
A correct management of the space therefore consists in particular in detecting the tracks corresponding to one and the same object and in associating these tracks to benefit from their complementarity in terms of information.
However, the combination of these various observations is not immediate. In fact, the passive radar forms, with each utility transmitter, a bistatic base that is independent of the other bases, and the information generated, notably the position and speed information, is referenced in the “transmitter-radar” coordinate system associated with this base. Consequently, to be able to jointly exploit the information generated by each of the bistatic bases and relating to one and the same object, it is necessary to determine which of the available information can be attributed to this same object and can consequently be associated.
The general problem that is posed therefore consists in finding a means of automatically making the association of the bistatic blips delivered on the various reception channels, and/or various bistatic bases, which correspond to one and the same object, and of providing the radar management member with a set of global tracks in which each track represents a various object.